Remote-control system



May 22, 1945- G. WQBAUGHMAN l I REMOTE CONTROLVSYSTEM Filed Dec. 8, 1942 Patented May 22, 1945 REMOTE.- CONTROL SYSTEM George W. Baughman, Swissvale, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application December 8, 1942, Serial No. 468,224

12 Claims.

My invention relates to improvementsin remote control systems of the type in which impulse codes are transmitted between a central olice and aplurality of distant stations, and more particul larly to apparatus for locating faults affecting the line circuits of such systems and for overcoming the effects of faults.

The prior practice in systems of this character has been generally to connect the line relays and transmitting contacts at the office and stations all in series with the line wires, as shown for example, in the Letters Patent of the United States No. 2,229,249, issued January 21, 1941, to L. V. Lewis, for Remote control systems. A series line circuit has the advantage that a cross or short circuit occurring in the portion of the line circuit leading into any station usually has only a local eilect, and in any case does not prevent the system from being maintained in operation between the office and all stations on Athe cnice side of the fault. On the other hand, a break in a series line circuit at any point, in the absence of suitable fault detecting means, such for example, as that shown in my Letters Patent of the United States No. 2,011,237, issued August 13, 1935, results in the total disablement of the system.

More recently it has been found of advantage to connect the line relays and transmitting contacts of the remote control system in parallel rather than in series with the' line to facilitate the joint use of the line wires without interference by other communication facilities such as the telephone and telegraph, as shown, for example, in Letters Patent of the United States to Baughman et al., No. 2,303,875, issued December 1, 1942. It is inherent in a bridged line circuit that in the event of a break in the line the system remains operative .between the oice and the location of the break, and it follows that fault detecting apparatus of the sectionalizing type as shown in my prior patent is not applicable.

The object of my present invention is the provision of fault detecting apparatus analogous to that of my prior patent but applicable to such bridged line circuit systems. A further object is to provide means manually controllable from the central oftlce for isolating any station from the system in the event a faultat that station causes interference with the transmission of codes from other stations.

I shall describe one form of apparatus embodya typical bridged line circuit comprising the line wires Y and Z and the apparatus associated therewith located at the oice and at one station, it being understood that in general the circuit will include a number of such stations each having similar connections to the -line wires. The remote control apparatus as shown corresponds generally to the above-mentioned Lewis patent modified as shown in Fig. 1 of the Baughman et al. patent, together with two relays RP and RPP and a resistor W2 at each station, and a manual switch K at the oflice, added in accordance with the present invention.

For an understanding of the various details of operation of the remote control system, reference may be made to these patents, but for an understanding of the present invention it is believed that it will sufce to point out that the line wires are normally energized by current from an ofce battery 80, the positive terminal being normally connected to line wire Y and the negative terminal to line wire Z over back contacts b and d oi' a pole changer relay PC and of an oice transmitter relay OT, through a low pass Iilter l2.

At each station, a line relay R, of the high resistance biased polar type, is bridged across the line in series with a resistor Wl, the connections including back contacts :i and k of a station master relay M and the coils of a low pass lter I2 similar to the one at the office. Relay R is normally energized to close its left-hand contact, when its left-hand terminal is positive, as is the case when the system is at rest and relays PC and M are both released.

Control codes aretransmitted by periodically interrupting the line current by the operation of the office transmitter relay OT, the code operation ofv which will be repeated by each station line relay as will be obvious.

The olce line relay OR is of the stick polar type, and is operated locally by means not shown, in response to control codes. In receiving indication codes relay OR is operated by impulses of alternately opposite polarity delivered by transformer! as the line current is varied, the variations being produced by shunting the line wires periodically by the operation of a station transmitter relay T. l The initiation ofv an indication code is effected by energizing a station starting relay ST, thereby energizing a master relay M over a circuit governed by two timing relays Ll and L2 and a relay E, which relays are controlled by relay R as in the hereinbefore referred to Lewis patent, both timing relays beingl released only when relay R is steadily energized, indicating that the line is free. Relay E serves to open the circuit for relay M in the event two or more transmitters are set into operation at the same time, as explained in the patent. As shown herein, the starting circuit controlled by relay ST has been modied in accordance with my invention by including therein a front contact b of relay RP. Assuming for the present that relays RP and RPP are both energized, it will be seen that in response to the operation of relay ST, a circuit will be completed from one terminal B of the local current source at contact b of relay RP through the master relay M to the other terminal C of the same source, as shown on the drawing. Relay M therefore picks up, closing its front contacts i and 1c to complete a connection between line Wires Y and Z over back contact a of relay LBP, and thereby .shunting relay R to cause it to release, the consequent increase in current delivered by battery 80 to the line causing the oice line relay OR to reverse. The initial reversal of relay OR causes relay PC to pick up thereby reversing the polarity of the current in theline in the manner explained in the Baughman etal patent, and relay R upon releasing, causes the energization of relays LI, L2, LB and LBP, relay LB holding relay M'picked up until relay I6 is operated atthe end of 4the code. Relay M upon picking up completes a circuit for the station transmitter relay T as shown in the Lewis patent, to set relayT into operation, and contact b of relay T shunts 1the line wires periodically and thereby governs the olce line relay OR in accordance with the code, relays PC,A LB and LBP also remaining picked up until the code is completed, Relay yR at the transmitting station responds to the code because of the reversal of its connections to the line by the operation of the pole changercontacts y' and k of relay M, while ateach other station at which relay M has not been operated relayR will remain released until the line polarity is restored to normal by the. release of relay PC at the end of the code.

The connections of the .station filter I2 as shown differ from those at the oice, in that the lter condensersare normally disconnectedj that is to say, they are connected across the line lover front contacts h and 7' of relay M only during the transmission of an indication vcode from the corresponding station. The impedance across the line presented normally to voice frequency current by the station apparatus is thereby'materially increased, this arrangement being disclosed in a copending application for Letters Patent of the United States, Serial No. 401,092, led July 5, 1941, by G. W. Baughman et al., for Remote control systems. Y

Referring now to the apparatus of my invention,.relay RP, as will be clear from the drawing, functions as a stick repeater of relay R and the fault relay RPP is a repeater of relay RP. Relay RP has a pick-up circuit closed in response to the operation of the station deliveryrelay D, and a holding circuit which closes when relay RP picks up and relay RPP is thereby energized. Relay D functions as shown in Fig. 7 of the abovementioned Lewis patent; that is, it operates, and consequently picks up relay RP in response to the receipt of the final delivery step of a control code transmitted from the office to the particular station shown. Relay RP upon picking up, completes atits contact a, the energizing circuit for relayY RPP, and relay RPP then picks up to y complete at its contact b the holding circuit for relay RP extending to terminal B at vthe normally closed left-hand contact of the station line relay R. Relay RP is therefore normally energized, and likewise relay RPP; relay RP is operated repeatedly in'accordance with the code operation of relay R, as long as relay RPP remains picked up. In normal operation, the longest interval of release yof relay R andconsequently of relay RP is that required for thetransmission of an indication code by another station as above explained, this interval being in practice about three seconds. Thus during the transmission of a series of codes relay RPP will be repeatedly energized if the associated relay R responds to the code and otherwise willbe energized momentarily at intervals of threeseconds. Relay RPP is arranged to remain picked up under these conditions by the provision of an electrolytic condenser CI connected across its terminals whichprovides suflicient energy storage to cause relay -RPP to have a release period of from five to ten seconds. Relay RPP Will release therefore only when relay R has been released for an abnormal lengthof time, as would be the case for example, ifl line wires Y and Z were in contact due tc a fault.

If such a fault occurs within the station apparatus, its effect upon the remainder of the system Will be nullified by the release of relay RPP as will now be pointed out. The line circuit usually includes a large number of .relaysR in parallel and the impedance presented by each relay to the line is made relatively high in order to match their joint impedance with that 'of theline wires and to `render the shunts applied by the transmitter relays T more effective, by, connect ing an impedance unit or resistor Wl invseries with each relay R having ,an impedance value usually several times that of the relay winding. The added impedance unitor resistorWZ is of the same value as Wl, but is normally, short circuited by front contact a of relay RPP.y It will be seen that when relay RPP is released, impedance unit WI, which is located between-.the station transmitting apparatus and relay R,l becomes short circuited by theclosing of back contact c of relay RPP and is replaced in the relay circuit by the similar impedancev unit W2 located between the Astationtransmitting .apparatus and the line, It follows that if a short circuit occurs connecting wires Y and Z together through the filter or station apparatus, so that relay R is shunted, relays R, RP and RPP will release, whereupon the impedance presented by the station apparatus to the line will again become'relatively high due to the insertion of the impedance unit W2 between this apparatus vand the line, to allow the remainder of thesystem to be operated in a normal manner. On the other hand,if relay R becomes steadily deenergized for any reason in the absence of a fault. in its line connections, the impedancev presented by the station apparatus to the line will remainl unchanged uponthe release of relay RPP, relay R remaining Ioperative and in condition to be reenergized and to then receive a control code whereby relay RPP may be reenergized, but the station will be rendered incapable of initiating an indication code, due to the release of relay RP, and the consequent opening of its front contact b in the station starting circuit.

The apparatus of my invention will thus clear a line fault automatically if it is due to a short circuit. at a station, y,after whichthe remainder of the system may be restored to operation by sending control codes to any other `stations which have been affected by thefault. i

The aparatus of my invention may also be controlled manually to clear a variety of faults other thanshort circuits. For example, the vlocal battery at a station may become discharged or other defects may develop to'render a station incapable of completing a code although able to initiate one repeatedly. Cut out devices of the thermal relaytype are usually provided to take care of situations of this kind, but such devices are also likely to fail tooperate as intended when the battery voltage is abnormally low.

In the event of improper operation of the system suspected to be due to afault at a field station, the central oiiice o-perator'in charge will open the key K for a period of at least iifteen seconds, opening its contact in the line circuit and thereby disconnecting the line battery 8i) to release the relays R, RP and RPP,lrendering all stations inactive, and then after closing key K to reenergize the relays R, he will send a control code to each station in turn to operate the delivery relays D andthereby pick up the relays RP and RPP. The operation of each relay D as explained in theLewis patent picks up the associated starting relay ST so that each control code is normally followed by an indication code from the called station. In the present instance this indictaion code informs the operator that relays RP and RPP have been picked up, since otherwise thev indication code would fail to be transmitted. If the location of the fault is already known, the control code for the offending station may be omitted so that it will remain isolated and in that case the above described operations result in restoring the remainder ofthe system to normal operation. On the other hand, if the location of the fault is not known, it may reap- Apear upon the delivery of a control code to a particular station, and its location being thereby made known, the fault may lbe cleared by repeating the above described operations, but omitting the code which caused the fault to reappear.

If the fault consists of a short circuit of the contacts of relay M or 'I' or the like, or if it is within the receiving apparatus which controls relay T so that it prevents the proper reception of a control code transmitted to the defective station, it is evident that one series of control codes will suflice both to identify the defective station and to restore the remainder of the system.

i In the event the voltage of the local source of current at a station fails gradually, less and less energy -will be stored by condenser CI and the release period of relay RPP will be shortened until a point is reached where relay RPP will release when a code is being transmitted from another station. Under these circumstances it is evident that a defective station may isolate itself from the system automatically.

Relay RPP is to be understood to be a slow release l.relay provided With the usual ferrules or short circuited winding to delay its release, and it will therefore function as an ordinary slow release relay in the event condenser Cl becomes disconnected. If this occurs, the maximum release period obtainable will normally be of the order of one second, allowing' relayRPP to drop out when another station transmits a code. If the station apparatus is otherwise in order the only loss will be its ability to initiate indication codes, and it may therefore be kept in operation until the defect is corrected by transmitting control Vcodes to the station, each such code resulting in the initiation of an indication code as already explained.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modificaitons may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

yHaving thus described my invention, what I claim is:

1. In a remote control system, an loiiloe and a station connected by line wires, a normally energized line circuit including a source of current at ,the oiflce, said line wires and a line relay connected across the line wires at the station, code transmitting apparatus at the station having a normally open transmitting contact included in a connection to said line wires, means including said code transmitting apparatus for closing said contact repeatedly for brief periods to shunt the line relay and thereby effect a periodic variation in the current flowin-g in said line wires, a fault relay at the station arranged to be actuated in response to a prolonged deenergization of said line relay, and means controlled by said fault relay when actuated for interposing an impedance in said connection to limit the current in the line wires to substantially its normal value even though said transmitting contact is closed, to thereby eiectively isolate the code transmitting apparatus from said line wires.

2. In a remote control system, an oflce and two stations connected by line wires, a normally energized line circuit including a source of current at the office, said line wires and a line relay connected across the line wires at each station, code transmitting and receiving apparatus at each station controlled by the line relay at that station, said transmitting apparatus having a normally open transmitting Contact included in a connection to said line wires, means controlled by each line relay when steadilyA energized for setting the associated code transmitting apparatus into operation to close its transmitting contact repeatedly for 'brief periods to shunt both f line relays and thereby effect a periodic variation in the current flowing in said line wires, a fault relay `at each station arranged to be actuated in response to a prolonged deenergization of the line relay at such station, means controlled by each fault relay when actuated for interposing an impedance in the connection between the line wires and said code transmitting apparatus at that station of suflicient value to prevent inter'- at the station, code transmitters at the ofce and station adapted to deliver impulse codes to said line wires at times to periodically deenergize said line relay, a fault relay at the station controlled locally by the line relay, means for picking up said fault relay responsive to the operation of said line relay in accordance with a particular code delivered by the oflice code transmitter,

means for releasing said fault relay effectively only whenthe'line'relay remains deenergized for a -predetermined time interval which isi longer' than any interval occurring during thetransmission of a series of said impulse codes, and' means preventing the initiation of a code by said station transmitter except lwhen the fault relay is picked 4. -In a. remote Vcontrol system',` an oilic'ean'd 'a lstation connected by line vvires,` a normally energized line circuit including a source of current and a manually operable contact at said office, said line wires and: a line relay at said station, code transmitters at saidy oice and'station adapt;

' ed to deliver impulse'codes to saidline 4wires at times to periodically 'release said-line relay; a fault relay at the" station "controlled" by .said line relay, means for pickingup said fault'relay responsivev to the operation of said lineirelayin accordance `with a particular code delive'zredfby th'eolice code transmitter,v means for maintaining said fault relay picked up until said line relay is released for a time interval which is longer than occurs in -theA normal operation of said' code tranmitters whereby said faultrelay maybeselectively'released in response tothe' operation of said manually operablecontact, and means preventing the' initiation of a code by said 'station transmitter except whenthe fault relay is picked up and said line relay is steadily energized.

5. In a remote control system, an oiiieeand a plurality of stations connected by linev wiresga source of current at the oic'e connected to said line wires, code transmitting apparatus at each station including means for connecting said line Wires together to vary the current fromsaid'source l2 l actuated for short circuiting said impedance and interposing a similar impedance between the associatedcode transmitting apparatus'and said line Wires to effectively isolatei the';stationat which the fault occurs, and means responsivel to tlie'operation of each line relay in accordance With a distinctive code to pick up the corresponding fault relay.

6. In a remote control system, an oice and a plurality of 'stations connected byline`wir`es, -a code transmitter at each stationl adapted to be energized from a localy source of current for delivering impulse codes to said line wires, a line relay at each station responsive toi the codes" delivered to said line Wires for controlling `4the associated code transmitter, a fault relay at'eaclfl station, means for picking upeachlfault relay-in response 'to the'operation of the'fassociated line relay, timing means associated with each fault relay supplied with energy from said-local source each time the corresponding line relayis operated and adapted to eiect the'release of such fault relay during the normal operation of-the system in the event of an abnormal decrease in the voltage of the local source, Yand means responsive to the release of each fault relayfor eiectively isolating the associated code'transmitter from said line wires.

7. In a remote control system, an office and a plurality of stations connected by' line lwires,'a fault relayr at each station, a code transmitter at each station `having :a normally' opentransmitting contact lconnected-'across theline Wires in'serieswith animpedance unit of relatively high value, saidunit being shunted by a no'rmally closed contact of lsaid fault relay,4 a, line relay at each station-connected across the transmitting contact at such station-in series with a second impedance `unit -of relatively high value andA adapted tobe energized over said line wires, said second impedance .being adapted to be shunted by a normally open-contact of said fault relay, means'at theoffice for supplying current tothe line wires to maintain said linerelays normally energized,-means for initiating the operation -of said code transmittersone at a time to periodicallyclose theirI transmitting contacts to vdeliver impulse vcodes to thev line Wires to Which said line relays are responsive, timing means controlled by-eachV line relayeiective if such vrelay remains-deenergized for a time longer'than occurs inthe normal operation of said transmittingl contacts for actuating vthe associated fault relay to open said normally closed contact and to close'said normally open contact, and.' means formaintaining suchv fault relay in its' actuated position as long asthe associated Aline relay vremains deenergized 8f Inv 'a remote control system, an cnice and a plurality or stations connected by line wires, ya faultrelay-at'each station,' a code transmitter ateach station having a normally open transmitting contact connected across the line wires, aline relay-at'eacli station connected' across the transmittingA contact at suchfstation in series with an impedance unit of relatively high Value and adapted to be energized over said line wires; means at the ofcefor supplying current to the line Wires' tty-'maintain said line relays-normally energizedmeans for initiating the operation `of said code transmitters one at a time to periodically closetheir transmitting contactsto deliver impulse codes totheline Wires'to'which said line relays are responsive, timing means controlled by each line relay effective ii such rela-y remains deenergized'for a. ytime'longer than occurs in'the normal voperation For said contacts for actuating theassociated fault relay, means controlled by each fault relaywhenactuated-for removing the impedance unit from the circuit for the associatedline relay and for interposing a similar unit insaid circuit between the associated transmitting contact andv the line wires; and means for maintaining such fault relay in its actuated positi'on'until the associated line relay becomes energizedmverthe' circuit' includingV said second impedance-unit.'

9. In a remote control system, an cnice and a plurality of stations connected by linefwires',f' a fault' relayaltfeach'station, a codeltransmitter at each stationhav'ing a normally open transmitting-v contact-connected? across the line Wiresga line relay at each'station connected across the transmitting contact atsuchsta'tion andadapted'to be energized over said line Wires,` means 'at theoflicevforsupplying current to the line wires codesto'the lin'e wires to-Which said-line relays are responsive,` ytimingmeans `controlled by each lin'e Trelay for-.actuating the 'associated `fault -relay inthe eventx the associatedtransmitting contact=remains closedor is short circuited-andsuch line relayis thereby maintainedv in Iits-'released position for a predetermined time, means controlled by such fault relay when actuated for interposing an impedance unit in the circuit for the associated line relay between the associated transmitting contact and the line wires, such unit having an impedance value sufficient to render said closed contact or short circuit incapable of eilecting the release of the line relays at other stations, and means for maintaining each fault relay actuated until the associated line relay again becomes energized.

10. In a remote control system, an oiice and a plurality of stations ,connected by line wires, a normally energized line circuit including a source of current at the office, said line wires and a plurality of line relays connected in parallel across the line wires there being one such relay at each station, a code transmitter at each station having a transmitting contact operable at times to connect the line wires together inter'n mittently through an impedance of. relatively low value to periodically deenergize said plurality of line relays, a normally energized slow release relay at each station, a repeater relay at each station for repeating the operating of the associated line relay having an energizing circuit including front contacts of such line relay and of the associated slow release relay, an energizing circuit for each slow release relay including a front contact of the associated repeating relay effective to lenergized line relay at each station responsive to the codes delivered to the line wires for controlling the associated code transmitter, a normally energized fault relay at each station, a holding circuit at each station including a front contact of the fault relay and a normally closed Contact ofthe line relay at such station including means effective when the circuit is closed to hold the fault relay energized, energy storage means as sociated with each fault relay for maintaining such relay energized While its holding circuit is temporarily opened during the code operation of the associated line relay, means responsive to the release of each fault relay for effectively f isolating the associated code transmitter from said line Wires, a delivery relay controlled by each line relay, and means controlled by each delivery relay for picking up the associated fault relay y to complete the holding circuit for such relay.

12. In a remote control system, an oice and a plurality of stations connected by line Wires,

maintain the slow release relay picked up unless the repeater relay remains released for a time longer than occurs in the normaloperation of said transmitting contacts, a delivery relay controlled by each line relay, a circuit closed by each delivery relay when operated by the associated line relay for initially energizing the associated repeater relay to thereby energize the associated slow release relay, and means eiective when each slow release relay assumes its released position to interpose an impedance of relatively high value in the connection of the associated transmitting contact to the line wires to render the line relays at other stations nonresponsive to the closing or short circuiting of such contact.

11. In a remote control system, an cnice and a plurality of stations connected by line wires, a code transmitter at each station for delivering impulse codes to said line wires,v a normally v a normally energized line circuit including a source of current at the omce, said line wires and a line relay at each station, a code transmitter at each station for delivering impulse codes to said line wires, a fault relay at each station, means for holding each fault relay normally picked up, comprising a holding circuit controlled by front contacts of such fault relay and a contact closed when the associated line relay is picked up, together with energy storage means for maintaining such fault relay energized when its line relay is released for brief periods in response to said impulse codes, means responsive to the release of such fault relay for eiectively isolating the associated code transmitter from said line circuit, code responsive means controlled by each line relay for selectively pickup up each fault relay to establish its holding circuit, and means at said oiiice for manually isolating one or more of said code transmitters from said line circuit, comprising a manually operable contact for opening the line circuit temporarily to release the fault relays at all stations together with means for transmitting codes to selectively reenergize the fault relays controlling the remaining code transmitters associated with said line circuit.

GEORGE W. BAUGHMAN. 

